Stopping the beating heart of cancer: KRAS reviewed

Small molecules for Kirsten rat sarcoma viral oncogene homolog mutant cancers: Past, present, and future

Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations have been identified in more than 20% of human cancers as one of the most common oncogenes, especially in non-small cell lung, colorectal, and pancreatic cancers. KRAS regulates the activation of multiple proteins involved in cell growth and proliferation, such as extracellular regulated protein kinases and mammalian target of rapamycin, as a hub between the epidermal growth factor receptor (EGFR) and downstream MAPK and AKT pathways. However, due to the lack of a binding pocket, KRAS has long been considered an undruggable target in recent decades until the discovery of Sotorasib (AMG510). With the approval of Glecirasib (JAB-21822), there are three approved small molecule inhibitors of KRAS, all of which are KRAS G12C inhibitors. At the same time, the limited clinical benefits and rapid emergence of drug resistance to the approved inhibitors have also promoted the emergence of more therapeutics, such as tri-complexes and proteolysis-targeting chimeras (PROTAC). In this paper, we summarize the development of KRAS inhibitors (KRASG12C, KRASG12D, and KRASmulti inhibitors, PROTAC, and tri-complex) and discuss the challenges and opportunities in the discovery of KRAS inhibitors in the hope of providing insights into the development of novel medications for KRAS.

Discovery and Characterization of RP03707: A Highly Potent and Selective KRASG12D PROTAC

KRASG12D, the most prevalent oncogenic mutation in KRAS-associated tumors, represents a highly sought-after drug target for cancer treatment. In this study, we explored a KRASG12D protein degradation approach using the PROTAC technology for the treatment of KRASG12D mutant tumors. Through the rational design of the KRASG12D binder and proper selection of the linker and the E3 ligase ligand, we constructed PROTACs and identified RP03707 as a CRBN-involving, highly potent, and selective KRASG12D degrader. RP03707 effectively inhibits tumor cell growth in multiple KRASG12D cell lines. It also exhibits prolonged PK/PD effects and excellent efficacy in mouse CDX models bearing KRASG12D tumors, highlighting its potential for the treatment of KRASG12D-driven tumors in clinical settings.

Glecirasib, a Potent and Selective Covalent KRAS G12C Inhibitor Exhibiting Synergism with Cetuximab or SHP2 Inhibitor JAB-3312

SIGNIFICANCE

Glecirasib potently and selectively inhibits KRAS G12C and reduces ERK and AKT phosphorylation in KRAS G12C-mutant cancer cells, further inducing cell-cycle arrest and apoptosis. Glecirasib monotherapy leads to tumor regression in KRAS G12C-mutant animal models and shows synergistic effects with cetuximab or JAB-3312 (sitneprotafib).

From bench to bedside: murine models of inherited and sporadic brain arteriovenous malformations

Brain arteriovenous malformations are abnormal vascular structures in which an artery shunts high pressure blood directly to a vein without an intervening capillary bed. These lesions become highly remodeled over time and are prone to rupture. Historically, brain arteriovenous malformations have been challenging to treat, using primarily surgical approaches. Over the past few decades, the genetic causes of these malformations have been uncovered. These can be divided into (1) familial forms, such as loss of function mutations in TGF-β (BMP9/10) components in hereditary hemorrhagic telangiectasia, or (2) sporadic forms, resulting from somatic gain of function mutations in genes involved in the RAS-MAPK signaling pathway. Leveraging these genetic discoveries, preclinical mouse models have been developed to uncover the mechanisms underlying abnormal vessel formation, and thus revealing potential therapeutic targets. Impressively, initial preclinical studies suggest that pharmacological treatments disrupting these aberrant pathways may ameliorate the abnormal pathologic vessel remodeling and inflammatory and hemorrhagic nature of these high-flow vascular anomalies. Intriguingly, these studies also suggest uncontrolled angiogenic signaling may be a major driver in bAVM pathogenesis. This comprehensive review describes the genetics underlying both inherited and sporadic bAVM and details the state of the field regarding murine models of bAVM, highlighting emerging therapeutic targets that may transform our approach to treating these devastating lesions.

Selinexor as a Therapeutic Target: Advances in Non-small Cell and Small Cell Lung Cancer Treatment Strategies

Selinexor treats lung cancer, particularly non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC). This review summarizes the prevalence and types of lung cancer and emphasizes the challenges associated with current treatments like resistance and limited effectiveness. Selinexor is a selective inhibitor of nuclear export (SINE) that has emerged as a potential therapy that targets the nuclear export of tumor suppressor proteins. The mechanisms of selinexor, its potential in combination therapies, and challenges like side effects and drug resistance are explained in this review. Key findings highlight the effectiveness of selinexor in preclinical studies, particularly against KRAS-mutant NSCLC and in combination with chemotherapy for SCLC. The review concludes with a discussion of future directions and underscores the potential of selinexor to improve the treatment strategies for lung cancer.

Performance evaluation of a CRISPR Cas9-based selective exponential amplification assay for the detection of KRAS mutations in plasma of patients with advanced pancreatic cancer

AIMS

Pancreatic ductal adenocarcinoma (PDAC) is highly malignant, with shockingly mortality rates. KRAS oncoprotein is the main molecular target for PDAC. Liquid biopsies, such as the detection of circulating tumour DNA (ctDNA), offer a promising approach for less invasive diagnosis. In this study, we aim to evaluate the precision and utility of programmable enzyme-based selective exponential amplification (PASEA) assay for rare mutant alleles identification.

METHODS

PASEA uses CRISPR-Cas9 to continuously shear wild-type alleles during recombinase polymerase amplification, while mutant alleles are exponentially amplified, ultimately reaching a level detectable by Sanger sequencing. We applied PASEA to detect KRAS mutations in plasma ctDNA. A total of 153 patients with stage IV PDAC were enrolled. We investigated the relationship between ctDNA detection rates with various clinical factors.

RESULTS

Our results showed 91.43% vs 44.83% detection rate in patients of prechemotherapy and undergoing chemotherapy. KRAS ctDNA was more prevalent in patients with liver metastases and patients did not undergo surgical resection. Patients with liver metastases prior to chemotherapy showed a sensitivity of 95.24% (20/21) with PASEA. Through longitudinal monitoring, we found ctDNA may be a more accurate biomarker for monitoring chemotherapy efficacy in PDAC than CA19-9.

CONCLUSIONS

Our study sheds light on the potential of ctDNA as a valuable complementary biomarker for precision targeted therapy, emphasising the importance of considering chemotherapy status, metastatic sites and surgical history when evaluating its diagnostic potential in PDAC. PASEA technology provides a reliable, cost-effective and minimally invasive method for detecting ctDNA of PDAC.

Microsecond Molecular Dynamics Simulation to Gain Insight Into the Binding of MRTX1133 and Trametinib With KRASG12D Mutant Protein for Drug Repurposing

The Kirsten Rat Sarcoma (KRAS) G12D mutant protein is a primary driver of pancreatic ductal adenocarcinoma, necessitating the identification of targeted drug molecules. Repurposing of drugs quickly finds new uses, speeding treatment development. This study employs microsecond molecular dynamics simulations to unveil the binding mechanisms of the FDA-approved MEK inhibitor trametinib with KRASG12D, providing insights for potential drug repurposing. The binding of trametinib was compared with clinical trial drug MRTX1133, which demonstrates exceptional activity against KRASG12D, for better understanding of interaction mechanism of trametinib with KRASG12D. The resulting stable MRTX1133-KRASG12D complex reduces root mean square deviation (RMSD) values, in Switch I and II domains, highlighting its potential for inhibiting KRASG12D. MRTX1133's robust interaction with Tyr64 and disruption of Tyr96-Tyr71-Arg68 network showcase its ability to mitigate the effects of the G12D mutation. In contrast, trametinib employs a distinctive binding mechanism involving P-loop, Switch I and II residues. Extended simulations to 1 μs reveal sustained network interactions with Tyr32, Thr58, and GDP, suggesting a role of trametinib in maintaining KRASG12D in an inactive state and impede the further cell signaling. The decomposition binding free energy values illustrate amino acids' contributions to binding energy, elucidating ligand-protein interactions and molecular stability. The machine learning approach reveals that van der Waals interactions among the residues play vital role in complex stability and the potential amino acids involved in drug-receptor interactions of each complex. These details provide a molecular-level understanding of drug binding mechanisms, offering essential knowledge for further drug repurposing and potential drug discovery.

Integrating allele-specific PCR with CRISPR-Cas13a for sensitive KRAS mutation detection in pancreatic cancer

BACKGROUND

The clustered regulatory interspaced short palindromic repeats (CRISPR)-Cas13a system has strong potential for highly sensitive detection of exogenous sequences. The detection of KRASG12 point mutations with low allele frequencies may prove powerful for the formal diagnosis of pancreatic ductal adenocarcinoma (PDAC).

RESULTS

We implemented preamplification of KRAS alleles (wild-type and mutant) to reveal the presence of mutant KRAS with CRISPR-Cas13a. The discrimination of KRASG12D from KRASWT was poor for the generic KRAS preamplification templates and depended on the crRNA design, the secondary structure of the target templates, and the nature of the mismatches between the guide and the templates. To improve the specificity, we used an allele-specific PCR preamplification method called CASPER (Cas13a Allele-Specific PCR Enzyme Recognition). CASPER enabled specific and sensitive detection of KRASG12D with low DNA input. CASPER detected KRAS mutations in DNA extracted from patients' pancreatic ultrasound-guided fine-needle aspiration fluid.

CONCLUSION

CASPER is easy to implement and is a versatile and reliable method that is virtually adaptable to any point mutation.

Identification and Characterization of Novel Small-Molecule Enhancers of the CUL3LZTR1 E3 Ligase KRAS Complex

The RAS family of GTPases is among the most frequently mutated proteins in human cancer, creating a high clinical demand for therapies that counteract their signaling activity. An important layer of regulation that could be therapeutically exploited is the proteostatic regulation of the main RAS GTPases KRAS, NRAS, and HRAS, as well as the closely related members, MRAS and RIT1, by the leucine zipper-like transcriptional regulator 1 cullin 3 RING E3 ubiquitin ligase complex (CUL3LZTR1). Genetic inactivation of LZTR1, as observed in different cancer entities and Noonan syndrome leads to enhanced RAS GTPase abundance and altered MAPK pathway activation state. Novel therapeutic approaches to interfere with hyperactive RAS signaling, thereby complementing existing treatments, are highly sought after. Motivated by the growing arsenal of molecular glue degraders, we report the identification of novel chemical fragments that enhance the protein-protein interaction (PPI) of the KRAS-LZTR1 complex. We established a split-luciferase-based reporter assay that monitors the RAS GTPase-LZTR1 interaction in a scalable format, capable of capturing chemical, as well as mutational perturbations. Using this screening system, in combination with a small fragment library, we identified two fragments, C53 and Z86, that enhance the interaction of the KRAS-LZTR1 complex in a dose-dependent manner. Further orthogonal validation experiments using proximity biotinylation (BioID), thermal shift assays, and NMR spectroscopy demonstrated fragment-dependent enhanced recruitment of endogenous LZTR1 and physical engagement of KRAS. The two fragments, which potentiate the KRAS-LZTR1 interaction, serve as starting points for fragment-based drug discovery. Additionally, the assay we introduced is amenable to high-throughput screening to further explore the pharmacological modulation of the CUL3LZTR1-RAS GTPase complex.

Targeting cancer with small-molecule pan-KRAS degraders

Mutations in the Kirsten rat sarcoma viral oncogene homolog (KRAS) protein are highly prevalent in cancer. However, small-molecule concepts that address oncogenic KRAS alleles remain elusive beyond replacing glycine at position 12 with cysteine (G12C), which is clinically drugged through covalent inhibitors. Guided by biophysical and structural studies of ternary complexes, we designed a heterobifunctional small molecule that potently degrades 13 out of 17 of the most prevalent oncogenic KRAS alleles. Compared with inhibition, KRAS degradation results in more profound and sustained pathway modulation across a broad range of KRAS mutant cell lines, killing cancer cells while sparing models without genetic KRAS aberrations. Pharmacological degradation of oncogenic KRAS was tolerated and led to tumor regression in vivo. Together, these findings unveil a new path toward addressing KRAS-driven cancers with small-molecule degraders.

Evaluation of KRAS inhibitor-directed therapies for pancreatic cancer treatment

Despite significant advancements in the treatment of other cancers, pancreatic ductal adenocarcinoma (PDAC) remains one of the world's deadliest cancers. More than 90% of PDAC patients harbor a Kirsten rat sarcoma (KRAS) gene mutation. Although the clinical potential of anti-KRAS therapies has long been realized, all initial efforts to target KRAS were unsuccessful. However, with the recent development of a new generation of KRAS-targeting drugs, multiple KRAS-targeted treatment options for patients with PDAC have entered clinical trials. In this review, we provide an overview of current standard of care treatment, describe RAS signaling and the relevance of KRAS mutations, and discuss RAS isoform- and mutation-specific differences. We also evaluate the clinical efficacy and safety of mutation-selective and multi-selective inhibitors, in the context of PDAC. We then provide a comparison of clinically relevant KRAS inhibitors to second-line PDAC treatment options. Finally, we discuss putative resistance mechanisms that may limit the clinical effectiveness of KRAS-targeted therapies and provide a brief overview of promising therapeutic approaches in development that are focused on mitigating these resistance mechanisms.

Design, synthesis, and evaluation of purine and pyrimidine-based KRAS G12D inhibitors: Towards potential anticancer therapy

Oncogenic RAS mutations, commonly observed in human tumors, affect approximately 30% of cancer cases and pose a significant challenge for effective cancer treatment. Current strategies to inhibit the KRAS G12D mutation have shown limited success, emphasizing the urgent need for new therapeutic approaches. In this study, we designed and synthesized several purine and pyrimidine analogs as inhibitors for the KRAS G12D mutation. Our synthesized compounds demonstrated potent anticancer activity against cell lines with the KRAS G12D mutation, effectively impeding their growth. They also exhibited low toxicity in normal cells, indicating their selective action against cancer cells harboring the KRAS G12D mutation. Notably, the lead compound, PU1-1 induced the programmed cell death of KRAS G12D-mutated cells and reduced the levels of active KRAS and its downstream signaling proteins. Moreover, PU1-1 significantly shrunk the tumor size in a pancreatic xenograft model induced by the KRAS G12D mutation, further validating its potential as a therapeutic agent. These findings highlight the potential of purine-based KRAS G12D inhibitors as candidates for targeted cancer therapy. However, further exploration and optimization of these compounds are essential to meet the unmet clinical needs of patients with KRAS-mutant cancers.

Emerging Therapies in Kirsten Rat Sarcoma Virus (+) Non-Small-Cell Lung Cancer

Kirsten rat sarcoma virus (KRAS) is the most frequently found oncogene in human cancers, including non-small-cell lung cancer (NSCLC). For many years, KRAS was considered "undruggable" due to its structure and difficult targeting. However, the discovery of the switch II region in the KRAS-G12C-mutated protein has changed the therapeutic landscape with the design and development of novel direct KRAS-G12C inhibitors. Sotorasib and adagrasib are FDA-approved targeted agents for pre-treated patients with KRAS-G12C-mutated NSCLC. Despite promising results, the efficacy of these novel inhibitors is limited by mechanisms of resistance. Ongoing studies are evaluating combination strategies for overcoming resistance. In this review, we summarize the biology of the KRAS protein and the characteristics of KRAS mutations. We then present current and emerging therapeutic approaches for targeting KRAS mutation subtypes intending to provide individualized treatment for lung cancer harboring this challenging driver mutation.

Biophysical and Biochemical Characterization of Structurally Diverse Small Molecule Hits for KRAS Inhibition

We describe six compounds as early hits for the development of direct inhibitors of KRAS, an important anticancer drug target. We show that these compounds bind to KRAS with affinities in the low micromolar range and exert different effects on its interactions with binding partners. Some of the compounds exhibit selective binding to the activated form of KRAS and inhibit signal transduction through both the MAPK or the phosphatidylinositide 3-kinase PI3K-protein kinase B (AKT) pathway in cells expressing mutant KRAS. Most inhibit intrinsic and/or SOS-mediated KRAS activation while others inhibit RAS-effector interaction. We propose these compounds as starting points for the development of non-covalent allosteric KRAS inhibitors.

Identification of novel peptide inhibitors for the KRas-G12C variant to prevent oncogenic signaling

Kirsten rat sarcoma viral oncogene homolog (KRas) activating mutations are common in solid tumors, accounting for 90%, 45%, and 35% of pancreatic, colorectal, and lung cancers (LC), respectively. Each year, nearly 150k new cases (both men and women) of KRas-mutated malignancies are reported in the United States. NSCLC (non-small cell lung cancer) accounts for 80% of all LC cases. KRas mutations are found in 15% to 25% of NSCLC patients. The main cause of NSCLC is the KRas-G12C mutation. The drugs Sotorasib and Adagrasib were recently developed to treat advanced NSCLC caused by the KRas-G12C mutation. Most patients do not respond to KRas-G12C inhibitors due to cellular, molecular, and genetic resistance. Because of their safety, efficacy, and selectivity, peptide inhibitors have the potential to treat newly developing KRas mutations. Based on the KRas mutations, peptide inhibitors that are highly selective and specific to individual lung cancers can be rationally designed. The current study uses an alanine and residue scanning approach to design peptide inhibitors for KRas-G12C based on the known peptide. Our findings show that substitution of F3K, G11T, L8C, T14C, K13D, G11S, and G11P considerably enhances the binding affinity of the novel peptides, whereas F3K, G11T, L8C, and T14C peptides have higher stability and favorable binding to the altered peptides. Overall, our study paves the road for the development of potential therapeutic peptidomimetics that target the KRas-G12C complex and may inhibit the KRas and SOS complex from interacting.Communicated by Ramaswamy H. Sarma.

Prognostic Role of KRAS G12C Mutation in Non-Small Cell Lung Cancer: A Systematic Review and Meta-Analysis

KRAS G12C mutation (mKRAS G12C) is the most frequent KRAS point mutation in non-small cell lung cancer (NSCLC) and has been proven to be a predictive biomarker for direct KRAS G12C inhibitors in advanced solid cancers. We sought to determine the prognostic significance of mKRAS G12C in patients with NSCLC using the meta-analytic approach. A protocol is registered at the International Prospective Register for systematic reviews (CRD42022345868). PubMed, EMBASE, The Cochrane Library, and Clinicaltrials.gov.in were searched for prospective or retrospective studies reporting survival data for tumors with mKRAS G12C compared with either other KRAS mutations or wild-type KRAS (KRAS-WT). The hazard ratios (HRs) for overall survival (OS) or Disease-free survival (DFS) of tumors were pooled according to fixed or random-effects models. Sixteen studies enrolling 10,153 participants were included in the final analysis. mKRAS G12C tumors had poor OS [HR, 1.42; 95% CI, 1.10-1.84, p = 0.007] but similar DFS [HR 2.36, 95% CI 0.64-8.16] compared to KRAS-WT tumors. Compared to other KRAS mutations, mKRAS G12C tumors had poor DFS [HR, 1.49; 95% CI, 1.07-2.09, p < 0.0001] but similar OS [HR, 1.03; 95% CI, 0.84-1.26]. Compared to other KRAS mutations, high PD-L1 expression (>50%) [OR 1.37 95% CI 1.11-1.70, p = 0.004] was associated with mKRAS G12C tumors. mKRAS G12C is a promising prognostic factor for patients with NSCLC, negatively impacting survival. Prevailing significant heterogeneity and selection bias might reduce the validity of these findings. Concomitant high PD-L1 expression in these tumors opens doors for exciting therapeutic potential.

Tumor-intrinsic expression of the autophagy gene Atg16l1 suppresses anti-tumor immunity in colorectal cancer

Microsatellite-stable colorectal cancer (MSS-CRC) is highly refractory to immunotherapy. Understanding tumor-intrinsic determinants of immunotherapy resistance is critical to improve MSS-CRC patient outcomes. Here, we demonstrate that high tumor expression of the core autophagy gene ATG16L1 is associated with poor clinical response to anti-PD-L1 therapy in KRAS-mutant tumors from IMblaze370 (NCT02788279), a large phase III clinical trial of atezolizumab (anti-PD-L1) in advanced metastatic MSS-CRC. Deletion of Atg16l1 in engineered murine colon cancer organoids inhibits tumor growth in primary (colon) and metastatic (liver and lung) niches in syngeneic female hosts, primarily due to increased sensitivity to IFN-γ-mediated immune pressure. ATG16L1 deficiency enhances programmed cell death of colon cancer organoids induced by IFN-γ and TNF, thus increasing their sensitivity to host immunity. In parallel, ATG16L1 deficiency reduces tumor stem-like populations in vivo independently of adaptive immune pressure. This work reveals autophagy as a clinically relevant mechanism of immune evasion and tumor fitness in MSS-CRC and provides a rationale for autophagy inhibition to boost immunotherapy responses in the clinic.

Small-Molecule Inhibition of KRAS through Conformational Selection

Mutations in KRAS account for about 20% of human cancers. Despite the major progress in recent years toward the development of KRAS inhibitors, including the discovery of covalent inhibitors of the G12C KRAS variant for the treatment of non-small-cell lung cancer, much work remains to be done to discover broad-acting inhibitors to treat many other KRAS-driven cancers. In a previous report, we showed that a 308.4 Da small-molecule ligand [(2R)-2-(N'-(1H-indole-3-carbonyl)hydrazino)-2-phenyl-acetamide] binds to KRAS with low micro-molar affinity [Chem. Biol. Drug Des.2019; 94(2):1441-1456]. Binding of this ligand, which we call ACA22, to the p1 pocket of KRAS and its interactions with residues at beta-strand 1 and the switch loops have been supported by data from nuclear magnetic resonance spectroscopy and microscale thermophoresis experiments. However, the inhibitory potential of the compound was not demonstrated. Here, we show that ACA22 inhibits KRAS-mediated signal transduction in cells expressing wild type (WT) and G12D mutant KRAS and reduces levels of guanosine triphosphate-loaded WT KRAS more effectively than G12D KRAS. We ruled out the direct effect on nucleotide exchange or effector binding as possible mechanisms of inhibition using a variety of biophysical assays. Combining these observations with binding data that show comparable affinities of the compound for the active and inactive forms of the mutant but not the WT, we propose conformational selection as a possible mechanism of action of ACA22.

KRAS p.G12C Mutation in Metastatic Colorectal Cancer: Prognostic Implications and Advancements in Targeted Therapies

KRAS is frequently mutated in tumors. It is mutated in approximately 30% of all cancer cases and in nearly 50% of cases of metastatic colorectal cancer (CRC), which is the third leading cause of cancer-related deaths worldwide. Recent advancements in understanding CRC biology and genetics have highlighted the significance of KRAS mutations in the progression of CRC. The KRAS gene encodes a small GTPase (Guanosine TriPhosphatases) that plays a key role in signaling pathways associated with important proteins involved in amplifying growth factor and receptor signals. Mutations in KRAS are frequently observed in codons 12 and 13, and these mutations have oncogenic properties. Abnormal activation of KRAS proteins strongly stimulates signals associated with various cancer-related processes in CRC, including cell proliferation, migration and neoangiogenesis. In this review, we explore the distinct prognostic implications of KRAS mutations. Specifically, the KRAS p.G12C mutation is associated with a worse prognosis in metastatic CRC. The correlation between structure, conformation and mutations is visually presented to emphasize how alterations in individual amino acids at the same position in a single protein can unexpectedly exhibit complex involvement in cancer. Last, KRAS p.G12C is discussed as an emerging and promising therapeutic target in metastatic CRC, providing a concise overview of available clinical data regarding the use of new inhibitors.

A Case of Primary Intracranial Sarcoma, DICER1-Mutant, in a Child with a Germline DICER1 Mutation

DICER1 syndrome is a tumor predisposition syndrome caused by abnormal micro-RNA processing which leads to a variety of benign and malignant neoplasms in many organ systems, including the central nervous system. This paper reports the case of a primary intracranial sarcoma, DICER1-mutant, in a patient with a germline DICER1 variant thought most likely to be de novo. The patient is a ten-year-old boy who presented acutely with altered level of consciousness, emesis, and left-sided weakness. Imaging revealed a large right frontal hemorrhagic lesion, which was urgently debulked. Histology demonstrated a high-grade sarcomatous lesion. Molecular studies revealed compound heterozygous DICER1 variants (a frame shift insertion and a missense mutation), and a KRAS missense mutation. The final pathologic diagnosis was rendered to be "primary intracranial sarcoma, DICER1-mutant". Germline genetic testing revealed that the patient possessed a germline DICER1 variant (parental testing was negative). A dramatic reduction in tumor size was precipitated via chemotherapy (ifosfamide, carboplatin, and etoposide) and radiotherapy (focal proton beam therapy). There was no evidence of residual disease at the primary site at the end of the therapy.

Characteristic analysis and identification of novel molecular biomarkers in elderly glioblastoma patients using the 2021 WHO Classification of Central Nervous System Tumors

Introduction

Elderly glioblastoma (GBM) patients is characterized by high incidence and poor prognosis. Currently, however, there is still a lack of adequate molecular characterization of elderly GBM patients. The fifth edition of the WHO Classification of Central Nervous System Tumors (WHO5) gives a new classification approach for GBM, and the molecular characteristics of elderly GBM patients need to be investigated under this new framework.

Methods

The clinical and radiological features of patients with different classifications and different ages were compared. Potential prognostic molecular markers in elderly GBM patients under the WHO5 classification were found using Univariate Cox regression and Kaplan-Meier survival analysis.

Results

A total of 226 patients were included in the study. The prognostic differences between younger and elderly GBM patients were more pronounced under the WHO5 classification. Neurological impairment was more common in elderly patients (p = 0.001), while intracranial hypertension (p = 0.034) and epilepsy (p = 0.038) were more common in younger patients. Elderly patients were more likely to have higher Ki-67(p = 0.013), and in elderly WHO5 GBM patients, KMT5B (p = 0.082), KRAS (p = 0.1) and PPM1D (p = 0.055) were each associated with overall survival (OS). Among them, KRAS and PPM1D were found to be prognostic features unique to WHO5 elderly GBM patients.

Conclusion

Our study demonstrates that WHO5 classification can better distinguish the prognosis of elderly and younger GBM. Furthermore, KRAS and PPM1D may be potential prognostic predictors in WHO5 elderly GBM patients. The specific mechanism of these two genes in elderly GBM remains to be further studied.

Overall survival in patients with advanced non-small cell lung cancer with KRAS G12C mutation with or without STK11 and/or KEAP1 mutations in a real-world setting

BACKGROUND

KRAS mutations occur frequently in advanced non-small cell lung cancer (aNSCLC); the G12C mutation is the most prevalent. Alterations in STK11 or KEAP1 commonly co-occur with KRAS mutations in aNSCLC. Using real-world data, we assessed the effect of KRAS G12C mutation with or without STK11 and/or KEAP1 mutations on overall survival (OS) in patients with aNSCLC receiving cancer immunotherapy (CIT), chemotherapy, or both in first line (1L) and second line (2L).

METHODS

Patients diagnosed with aNSCLC between January 2011 and March 2020 in a clinico-genomic database were included. Cox proportional hazards models adjusted for left truncation, baseline demographics and clinical characteristics were used to analyze the effect of STK11 and/or KEAP1 co-mutational status on OS in patients with KRAS wild-type (WT) or G12C mutation.

RESULTS

Of 2715 patients with aNSCLC without other actionable driver mutations, 1344 (49.5%) had KRAS WT cancer, and 454 (16.7%) had KRAS G12C-positive cancer. At 1L treatment start, significantly more patients with KRAS G12C-positive cancer were female, smokers, and had non-squamous histology, a higher prevalence of metastasis and programmed death-ligand 1 positivity than those with KRAS WT cancer. Median OS was comparable between patients with KRAS G12C-positive and KRAS WT cancer when receiving chemotherapy or combination CIT and chemotherapy in the 1L or 2L. Median OS was numerically longer in patients with KRAS G12C vs KRAS WT cancer treated with 1L CIT (30.2 vs 10.6 months, respectively) or 2L CIT (11.3 vs 7.6 months, respectively). Co-mutation of STK11 and KEAP1 was associated with significantly shorter OS in patients receiving any type of 1L therapy, regardless of KRAS G12C mutational status.

CONCLUSIONS

This real-world study showed that patients with KRAS G12C-positive or KRAS WT cancer have similar OS in the 1L or 2L when treated with chemotherapy or combination CIT and chemotherapy. In contrast to aNSCLC patients with EGFR or ALK driver mutations, patients with KRAS G12C-positive cancer may benefit from CIT monotherapy. Co-mutation of STK11 and KEAP1 was associated with significantly shorter survival, independent of KRAS G12C mutational status, reflecting the poor prognosis and high unmet need in this patient population.

TEAD Inhibitors Sensitize KRASG12C Inhibitors via Dual Cell Cycle Arrest in KRASG12C-Mutant NSCLC

KRASG12C is one of the most common mutations detected in non-small cell lung cancer (NSCLC) patients, and it is a marker of poor prognosis. The first FDA-approved KRASG12C inhibitors, sotorasib and adagrasib, have been an enormous breakthrough for patients with KRASG12C mutant NSCLC; however, resistance to therapy is emerging. The transcriptional coactivators YAP1/TAZ and the family of transcription factors TEAD1-4 are the downstream effectors of the Hippo pathway and regulate essential cellular processes such as cell proliferation and cell survival. YAP1/TAZ-TEAD activity has further been implicated as a mechanism of resistance to targeted therapies. Here, we investigate the effect of combining TEAD inhibitors with KRASG12C inhibitors in KRASG12C mutant NSCLC tumor models. We show that TEAD inhibitors, while being inactive as single agents in KRASG12C-driven NSCLC cells, enhance KRASG12C inhibitor-mediated anti-tumor efficacy in vitro and in vivo. Mechanistically, the dual inhibition of KRASG12C and TEAD results in the downregulation of MYC and E2F signatures and in the alteration of the G2/M checkpoint, converging in an increase in G1 and a decrease in G2/M cell cycle phases. Our data suggest that the co-inhibition of KRASG12C and TEAD leads to a specific dual cell cycle arrest in KRASG12C NSCLC cells.

Intracellular Delivery of Anti-Kirsten Rat Sarcoma Antibodies Mediated by Polymeric Micelles Exerts Strong In Vitro and In Vivo Anti-Tumorigenic Activity in Kirsten Rat Sarcoma-Mutated Cancers

The Kirsten rat sarcoma viral oncogene (KRAS) is one of the most well-known proto-oncogenes, frequently mutated in pancreatic and colorectal cancers, among others. We hypothesized that the intracellular delivery of anti-KRAS antibodies (KRAS-Ab) with biodegradable polymeric micelles (PM) would block the overactivation of the KRAS-associated cascades and revert the effect of its mutation. To this end, PM-containing KRAS-Ab (PM-KRAS) were obtained using Pluronic F127. The feasibility of using PM for antibody encapsulation as well as the conformational change of the polymer and its intermolecular interactions with the antibodies was studied, for the first time, using in silico modeling. In vitro, encapsulation of KRAS-Ab allowed their intracellular delivery in different pancreatic and colorectal cancer cell lines. Interestingly, PM-KRAS promoted a high proliferation impairment in regular cultures of KRAS-mutated HCT116 and MIA PaCa-2 cells, whereas the effect was neglectable in non-mutated or KRAS-independent HCT-8 and PANC-1 cancer cells, respectively. Additionally, PM-KRAS induced a remarkable inhibition of the colony formation ability in low-attachment conditions in KRAS-mutated cells. In vivo, when compared with the vehicle, the intravenous administration of PM-KRAS significantly reduced tumor volume growth in HCT116 subcutaneous tumor-bearing mice. Analysis of the KRAS-mediated cascade in cell cultures and tumor samples showed that the effect of PM-KRAS was mediated by a significant reduction of the ERK phosphorylation and a decrease in expression in the stemness-related genes. Altogether, these results unprecedently demonstrate that the delivery of KRAS-Ab mediated by PM can safely and effectively reduce the tumorigenicity and the stemness properties of KRAS-dependent cells, thus bringing up new possibilities to reach undruggable intracellular targets.

Targeting the 'Undruggable' Driver Protein, KRAS, in Epithelial Cancers: Current Perspective

This review summarizes recent development in synthetic drugs and biologics targeting intracellular driver genes in epithelial cancers, focusing on KRAS, and provides a current perspective and potential leads for the field. Compared to biologics, small molecule inhibitors (SMIs) readily penetrate cells, thus being able to target intracellular proteins. However, SMIs frequently suffer from pleiotropic effects, off-target cytotoxicity and invariably elicit resistance. In contrast, biologics are much larger molecules limited by cellular entry, but if this is surmounted, they may have more specific effects and less therapy-induced resistance. Exciting breakthroughs in the past two years include engineering of non-covalent KRAS G12D-specific inhibitor, probody bispecific antibodies, drug-peptide conjugate as MHC-restricted neoantigen to prompt immune response by T-cells, and success in the adoptive cell therapy front in both breast and pancreatic cancers.

Oncogenic RAS promotes MYC protein stability by upregulating the expression of the inhibitor of apoptosis protein family member Survivin

The small GTPase KRAS is frequently mutated in pancreatic cancer and its cooperation with the transcription factor MYC is essential for malignant transformation. The key to oncogenic KRAS and MYC working together is the stabilization of MYC expression due to KRAS activating the extracellular signal-regulated kinase 1/2, which phosphorylates MYC at serine 62 (Ser 62). This prevents the proteasomal degradation of MYC while enhancing its transcriptional activity. Here, we identify how this essential signaling connection between oncogenic KRAS and MYC expression is mediated by the inhibitor of apoptosis protein family member Survivin. This discovery stemmed from our finding that Survivin expression is downregulated upon treatment of pancreatic cancer cells with the KRASG12C inhibitor Sotorasib. We went on to show that oncogenic KRAS increases Survivin expression by activating extracellular signal-regulated kinase 1/2 in pancreatic cancer cells and that treating the cells either with siRNAs targeting Survivin or with YM155, a small molecule that potently blocks Survivin expression, downregulates MYC and strongly inhibited their growth. We further determined that Survivin protects MYC from degradation by blocking autophagy, which then prevents cellular inhibitor of protein phosphatase 2A from undergoing autophagic degradation. Cellular inhibitor of protein phosphatase 2A, by inhibiting protein phosphatase 2A, helps to maintain MYC phosphorylation at Ser 62, thereby ensuring its cooperation with oncogenic KRAS in driving cancer progression. Overall, these findings highlight a novel role for Survivin in mediating the cooperative actions of KRAS and MYC during malignant transformation and raise the possibility that targeting Survivin may offer therapeutic benefits against KRAS-driven cancers.

Combined KRASG12C and SOS1 inhibition enhances and extends the anti-tumor response in KRASG12C-driven cancers by addressing intrinsic and acquired resistance

Efforts to improve the anti-tumor response to KRASG12C targeted therapy have benefited from leveraging combination approaches. Here, we compare the anti-tumor response induced by the SOS1-KRAS interaction inhibitor, BI-3406, combined with a KRASG12C inhibitor (KRASG12Ci) to those induced by KRASG12Ci alone or combined with SHP2 or EGFR inhibitors. In lung cancer and colorectal cancer (CRC) models, BI-3406 plus KRASG12Ci induces an anti-tumor response stronger than that observed with KRASG12Ci alone and comparable to those by the other combinations. This enhanced anti-tumor response is associated with a stronger and extended suppression of RAS-MAPK signaling. Importantly, BI-3406 plus KRASG12Ci treatment delays the emergence of acquired adagrasib resistance in both CRC and lung cancer models and is associated with re-establishment of anti-proliferative activity in KRASG12Ci-resistant CRC models. Our findings position KRASG12C plus SOS1 inhibition therapy as a promising strategy for treating both KRASG12C-mutated tumors as well as for addressing acquired resistance to KRASG12Ci.

PPDPF Promotes the Development of Mutant KRAS-Driven Pancreatic Ductal Adenocarcinoma by Regulating the GEF Activity of SOS1

The guanine nucleotide exchange factor (GEF) SOS1 catalyzes the exchange of GDP for GTP on RAS. However, regulation of the GEF activity remains elusive. Here, the authors report that PPDPF functions as an important regulator of SOS1. The expression of PPDPF is significantly increased in pancreatic ductal adenocarcinoma (PDAC), associated with poor prognosis and recurrence of PDAC patients. Overexpression of PPDPF promotes PDAC cell growth in vitro and in vivo, while PPDPF knockout exerts opposite effects. Pancreatic-specific deletion of PPDPF profoundly inhibits tumor development in KRASG12D -driven genetic mouse models of PDAC. PPDPF can bind GTP and transfer GTP to SOS1. Mutations of the GTP-binding sites severely impair the tumor-promoting effect of PPDPF. Consistently, mutations of the critical amino acids mediating SOS1-PPDPF interaction significantly impair the GEF activity of SOS1. Therefore, this study demonstrates a novel model of KRAS activation via PPDPF-SOS1 axis, and provides a promising therapeutic target for PDAC.

KRAS Inhibitor that Simultaneously Inhibits Nucleotide Exchange Activity and Effector Engagement

We describe a small molecule ligand ACA-14 (2-hydroxy-5-{[(2-phenylcyclopropyl) carbonyl] amino} benzoic acid) as an initial lead for the development of direct inhibitors of KRAS, a notoriously difficult anticancer drug target. We show that the compound binds to KRAS near the switch regions with affinities in the low micromolar range and exerts different effects on KRAS interactions with binding partners. Specifically, ACA-14 impedes the interaction of KRAS with its effector Raf and reduces both intrinsic and SOS-mediated nucleotide exchange rates. Likely as a result of these effects, ACA-14 inhibits signal transduction through the MAPK pathway in cells expressing mutant KRAS and inhibits the growth of pancreatic and colon cancer cells harboring mutant KRAS. We thus propose compound ACA-14 as a useful initial lead for the development of broad-acting inhibitors that target multiple KRAS mutants and simultaneously deplete the fraction of GTP-loaded KRAS while abrogating the effector-binding ability of the already GTP-loaded fraction.

Enhancing an Oxidative "Trojan Horse" Action of Vitamin C with Arsenic Trioxide for Effective Suppression of KRAS-Mutant Cancers: A Promising Path at the Bedside

The turn-on mutations of the KRAS gene, coding a small GTPase coupling growth factor signaling, are contributing to nearly 25% of all human cancers, leading to highly malignant tumors with poor outcomes. Targeting of oncogenic KRAS remains a most challenging task in oncology. Recently, the specific G12C mutant KRAS inhibitors have been developed but with a limited clinical outcome because they acquire drug resistance. Alternatively, exploiting a metabolic breach of KRAS-mutant cancer cells related to a glucose-dependent sensitivity to oxidative stress is becoming a promising indirect cancer targeting approach. Here, we discuss the use of a vitamin C (VC) acting in high dose as an oxidative "Trojan horse" agent for KRAS-mutant cancer cells that can be potentiated with another oxidizing drug arsenic trioxide (ATO) to obtain a potent and selective cytotoxic impact. Moreover, we outline the advantages of VC's non-natural enantiomer, D-VC, because of its distinctive pharmacokinetics and lower toxicity. Thus, the D-VC and ATO combination shows a promising path to treat KRAS-mutant cancers in clinical settings.

Characterization of the binding of MRTX1133 as an avenue for the discovery of potential KRASG12D inhibitors for cancer therapy

The Kirsten rat sarcoma (KRAS) oncoprotein has been on drug hunters list for decades now. Initially considered undruggable, recent advances have successfully broken the jinx through covalent inhibition that exploits the mutated cys12 in the switch II binding pocket (KRAS^G12C). Though this approach has achieved some level of success, patients with mutations other than cys12 are still uncatered for. KRAS^G12D is the most frequent KRAS mutated oncoprotein. It is only until recently, MRTX1133 has been discovered as a potential inhibitor of KRAS^G12D. This study seeks to unravel the structural binding mechanism of MRTX1133 as well as identify potential drug leads of KRAS^G12D based on structural binding characteristics of MRTX1133. It was revealed that MRTX1133 binding stabilizes the binding site by increasing the hydrophobicity which resultantly induced positive correlated movements of switches I and II which could disrupt their interaction with effector and regulatory proteins. Furthermore, MRTX1133 interacted with critical residues; Asp69 (- 4.54 kcal/mol), His95 (- 3.65 kcal/mol), Met72 (- 2.27 kcal/mol), Thr58 (- 2.23 kcal/mol), Gln99 (- 2.03 kcal/mol), Arg68 (- 1.67 kcal/mol), Tyr96 (- 1.59 kcal/mol), Tyr64 (- 1.34 kcal/mol), Gly60 (- 1.25 kcal/mol), Asp12 (- 1.04 kcal/mol), and Val9 (- 1.03 kcal/mol) that contributed significantly to the total free binding energy of - 73.23 kcal/mol. Pharmacophore-based virtual screening based on the structural binding mechanisms of MRTX1133 identified ZINC78453217, ZINC70875226 and ZINC64890902 as potential KRAS^G12D inhibitors. Further, structural optimisations and biochemical testing of these compounds would assist in the discovery of effective KRAS^G12D inhibitors.

Light at the end of the tunnel: Clinical features and therapeutic prospects of KRAS mutant subtypes in non-small-cell lung cancer

Lung cancer is one of the most common causes of cancer-related deaths, and non-small-cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancer cases. Kirsten rat sarcoma virus (KRAS), one of the three subtypes of the RAS family, is the most common oncogene involved in human cancers and encodes the key signaling proteins in tumors. Oncogenic KRAS mutations are considered the initiating factors in 30% of NSCLC cases, accounting for the largest proportion of NSCLC cases associated with driver mutations. Because effective inhibition of the related functions of KRAS with traditional small-molecule inhibitors is difficult, the KRAS protein is called an "undruggable target." However, in recent years, the discovery of a common mutation in the KRAS gene, glycine 12 mutated to cysteine (G12C), has led to the design and synthesis of covalent inhibitors that offer novel strategies for effective targeting of KRAS. In this review, we have summarized the structure, function, and signal transduction pathways of KRAS and discussed the available treatment strategies and potential treatment prospects of KRAS mutation subtypes (especially G12C, G12V, and G12D) in NSCLC, thus providing a reference for selecting KRAS mutation subtypes for the treatment of NSCLC.

Application of histology-agnostic treatments in metastatic colorectal cancer

Cancer treatment is increasingly focused on targeting molecular alterations identified across different tumor histologies. While some oncogenic drivers such as microsatellite instability (MSI) and NTRK fusions are actionable with the very same approach regardless of tumor type ("histology-agnostic"), others require histology-specific therapeutic adjustment ("histology-tuned") by means of adopting specific inhibitors and ad hoc combinations. Among histology-agnostic therapies, pembrolizumab or dostarlimab demonstrated comparable activity in MSI metastatic colorectal cancer (mCRC) as in other tumors with MSI status (ORR 38% vs 40% and 36% vs 39%, respectively), while entrectinib or larotrectinib proved effective in NTRK rearranged mCRC even though less dramatically than in the overall population (ORR 20% vs 57%, and 50% vs 78%, respectively). Histology-tuned approaches in mCRC are those targeting BRAF^V600E mutations and ERBB2 amplification, highlighting the need of simultaneous anti-EGFR blockade or careful choice of companion inhibitors in this tumor type. Anti-RET and anti-ALK therapies emerged as a potential histology-agnostic indications, while anti-KRAS^G12C strategies could develop as future histology-tuned therapies. Targeting of ERBB2 mutations and NRG1 fusion provided discrepant results. In conclusion, agnostic targets such as MSI and NTRK fusions are already exploitable in mCRC, while the plethora of emerging histology-tuned targets represent a challenging opportunity requiring concurrent evolution of molecular diagnostic tools.

Identification of lung cancer drivers by comparison of the observed and the expected numbers of missense and nonsense mutations in individual human genes

Largely, cancer development is driven by acquisition and positive selection of somatic mutations that increase proliferation and survival of tumor cells. As a result, genes related to cancer development tend to have an excess of somatic mutations in them. An excess of missense and/or nonsense mutations in a gene is an indicator of its cancer relevance. To identify genes with an excess of potentially functional missense or nonsense mutations one needs to compare the observed and expected numbers of mutations in the gene. We estimated the expected numbers of missense and nonsense mutations in individual human genes using (i) the number of potential sites for missense and nonsense mutations in individual transcripts and (ii) histology-specific nucleotide context-dependent mutation rates. To estimate mutation rates defined as the number of mutations per site per tumor we used silent mutations reported in the Catalog Of Somatic Mutations In Cancer (COSMIC). The estimates were nucleotide context dependent. We have identified 26 genes with an excess of missense and/or nonsense mutations for lung adenocarcinoma, 18 genes for small cell lung cancer, and 26 genes for squamous cell carcinoma of the lung. These genes include known genes and novel lung cancer gene candidates.

Inside the cracked kernel: establishing the molecular basis of AMG510 and MRTX849 in destabilising KRASG12C mutant switch I and II in cancer treatment

The Kirsten rat sarcoma oncoprotein (KRAS) has been punctuated by drug development failures for decades due to frequent mutations that occur mostly at codon 12 and the seemingly intractable targeting of the protein. However, with advances in covalent targeting, the oncoprotein is being expunged from the 'undruggable' list of proteins. This feat has seen some covalent drugs at different stages of clinical trials. The advancement of AMG510 and MRTX849 as inhibitors of cysteine mutated KRAS (KRAS^G12C) to phase-III clinical trials informed the biased selection of AMG510 and MRTX849 for this study. Despite this advance, the molecular and atomistic modus operandi of these drugs is yet to come to light. In this study, we employed computational tools to unravel the atomistic interactions and subsequent conformational effects of AMG510 and MRTX849 on the mutant KRAS^G12C. It was revealed that AMG510 and MRTX849 complexes presented similar total free binding energies, (ΔG_bind), of -88.15 ± 5.96 kcal/mol and -88.71 ± 7.70 kcal/mol, respectively. Gly10, Lys16, Thr58, Gly60, Glu62, Glu63, Arg68, Asp69, Met72, His95, Tyr96, Gln99, Arg102 and Val103 interacted prominently with AMG510 and MRTX849. These residues interacted with the pharmacophoric moieties of AMG510 and MRTX849 via hydrogen bonds with decreasing bond lengths at various stages of the simulation. These interactions together with pi-pi stacking, pi-sigma and pi-alkyl interactions induced unfolding of switch I whiles compacting switch II, which could interrupt the binding of effector proteins to these interfaces. These insights present useful atomistic perspectives into the success of AMG510 and MRTX849 which could guide the design of more selective and potent KRAS inhibitors.Communicated by Ramaswamy H. Sarma.

RHOA takes the RHOad less traveled to cancer

RAS and RHO GTPases function as signaling nodes that regulate diverse cellular processes. Whereas RAS mutations were identified in human cancers nearly four decades ago, only recently have mutations in two RHO GTPases, RAC1 and RHOA, been identified in cancer. RAS mutations are found in a diverse spectrum of human cancer types. By contrast, RAC1 and RHOA mutations are associated with distinct and restricted cancer types. Despite a conservation of RAS and RAC1 residues that comprise mutational hotspots, RHOA mutations comprise highly divergent hotspots. Whereas RAS and RAC1 act as oncogenes, RHOA may act as both an oncogene and a tumor suppressor. Thus, while RAS and RHO each take different mutational paths, they arrive at the same biological destination as cancer drivers.

Inhibitor of the Nuclear Transport Protein XPO1 Enhances the Anticancer Efficacy of KRAS G12C Inhibitors in Preclinical Models of KRAS G12C-Mutant Cancers

The identification of molecules that can bind covalently to KRAS G12C and lock it in an inactive GDP-bound conformation has opened the door to targeting KRAS G12C selectively. These agents have shown promise in preclinical tumor models and clinical trials. FDA has recently granted approval to sotorasib for KRAS G12C mutated non-small cell lung cancer (NSCLC). However, patients receiving these agents as monotherapy generally develop drug resistance over time. This necessitates the development of multi-targeted approaches that can potentially sensitize tumors to KRAS inhibitors. We generated KRAS G12C inhibitor-resistant cell lines and observed that they exhibit sensitivity toward selinexor, a selective inhibitor of nuclear export protein exportin1 (XPO1), as a single agent. KRAS G12C inhibitors in combination with selinexor suppressed the proliferation of KRAS G12C mutant cancer cell lines in a synergistic manner. Moreover, combined treatment of selinexor with KRAS G12C inhibitors resulted in enhanced spheroid disintegration, reduction in the number and size of colonies formed by G12C mutant cancer cells. Mechanistically, the combination of selinexor with KRAS G12C inhibitors suppressed cell growth signaling and downregulated the expression of cell cycle markers, KRAS and NF-kB as well as increased nuclear accumulation of tumor suppressor protein Rb. In an in vivo KRAS G12C cell-derived xenograft model, oral administration of a combination of selinexor and sotorasib was demonstrated to reduce tumor burden and enhance survival. In conclusion, we have shown that the nuclear transport protein XPO1 inhibitor can enhance the anticancer activity of KRAS G12C inhibitors in preclinical cancer models.

SIGNIFICANCE

In this study, combining nuclear transport inhibitor selinexor with KRAS G12C inhibitors has resulted in potent antitumor effects in preclinical cancer models. This can be an effective combination therapy for cancer patients that do not respond or develop resistance to KRAS G12C inhibitor treatment.

Resistance looms for KRAS G12C inhibitors and rational tackling strategies

KRAS mutations are one of the most frequent activating alterations in carcinoma. Recent efforts have witnessed a revolutionary strategy for KRAS G12C inhibitors with exhibiting conspicuous clinical responses across multiple tumor types, providing new impetus for renewed drug development and culminating in sotorasib with approximately 6-month median progression-free survival in KRAS G12C-driven lung cancer. However, diverse genomic and histological mechanisms conferring resistance to KRAS G12C inhibitors may limit their clinical efficacy. Herein, we first briefly discuss the recent resistance looms for KRAS G12C inhibitors, focusing on their clinical trials. We then comprehensively interrogate and underscore our current understanding of resistance mechanisms and the necessity of incorporating genomic analyses into the clinical investigation to further decipher resistance mechanisms. Finally, we highlight the future role of novel treatment strategies especially rational identification of targeted combinatorial approaches in tackling drug resistance, and propose our views on including the application of robust biomarkers to precisely guide combination medication regimens.

Anticipating resistance to KRAS inhibition: a novel role for USP21 in macropinocytosis regulation

This Outlook discusses the finding by Hou et al. describing the mechanism by which the deubiquitinase USP21 up-regulates the nutrient-scavenging process of macropinocytosis, rescuing PDAC cells from Kras extinction.

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers. Virtually all PDAC harbors an oncogenic mutation in the KRAS gene, making it the prime target for therapy. Most previous attempts to inhibit KRAS directly have been disappointing, but recent success in targeting some KRAS mutants presages a new era in PDAC therapy. Models of PDAC have predicted that identifying KRAS inhibitor resistance mechanisms will be critical. In this issue of Genes & Development, Hou and colleagues (pp. 1327–1332) identify one such mechanism in which the deubiquitinase USP21 up-regulates the nutrient-scavenging process of macropinocytosis, rescuing PDAC cells from Kras extinction.